1. Field of the Invention
The present invention relates to a liquid ejection head for printing by ejecting liquid, and a method of manufacturing the liquid ejection head, and specifically relates to an ink jet print head for printing by ejecting ink to a printing medium, and a method of manufacturing the ink jet print head.
2. Description of the Related Art
Usually, a liquid ejection head (hereinafter, also referred to as a print head) used in an inkjet printing apparatus includes an ejection port, a flow passage communicating with this ejection port, and a heat generating portion that generates, in this flow passage, heat energy used to eject ink. The heat generating portion comprises a heating resistor and an electrode for supplying electric power to the heating resistor. Usually, in the print head, in order to prevent electricity from conducting from the heat generating portion to ink, the heat generating portion is covered with a protective layer having an electrical insulation property. For example, a silicon nitride or the like is used as this protective layer. Because the heat generating portion is covered with a protective layer having an electrical insulation property and arranged in this manner, the electrical insulation of the heat generating portion from ink is secured.
Moreover, in the heat generating portion at the time of ejecting ink, a bubbling portion affecting bubbling is exposed to a high temperature due to the heating of the heating resistor in the heat generating portion. Then, at the time of ejecting ink, the heat generating portion will suffer, for example, a chemical action of the ink in combination with an impact due to cavitation phenomenon associated with the bubbling in the ink and the contraction of a bubble. For this reason, in the bubbling portion in the heat generating portion, a protective layer having an anti-cavitation property and an ink resistant property may be provided in a portion close to an ink reservoir so as to cover the bubbling portion. When ink is ejected by the print head, the surface of the protective layer adjacent to the ink reservoir is said to rise up to near 700° C. with the bubbling of the ink. Accordingly, in addition to the properties, such as good mechanical properties, chemical stability, and alkali resistance, this protective layer also requires heat resistance. From these required properties, noble metals, high-melting point transition metals, or alloys thereof have been proposed as the material used in the protective layer adjacent to the ink reservoir. Moreover, nitrides, oxides, silicides, and carbides of noble metals or high-melting point transition metals, or amorphous silicon, an amorphous alloy, and the like have been also proposed.
Among them, noble metals, such as iridium and platinum have been adopted as the protective layer arranged at a position adjacent to the ink reservoir because these are chemically stable and have a property of hardly reacting with ink. Japanese Patent Laid-Open No. 2007-269011 and Japanese Patent Laid-Open No. 2007-230127 disclose such a print head wherein a noble metal is used as the material of the protective layer arranged at the position adjacent to the ink reservoir.
FIG. 8A shows a cross sectional view of the ink jet print head disclosed in Japanese Patent Laid-Open No. 2007-269011. In the ink jet print head of Japanese Patent Laid-Open No. 2007-269011, a heat generating portion 102 is embedded and arranged at a position that allows heat energy to be transferred to the ink in a substrate 101. Then, a first protective layer 103 having an electrical insulation property is arranged so as to cover the heat generating portion 102. Moreover, a second protective layer 107 formed from a noble metal, the second protective layer 107 covering the first protective layer 103, is arranged at a portion adjacent to an ink flow passage in which ink is stored. Japanese Patent Laid-Open No. 2007-269011 enumerates silicon nitride as the material forming the first protective layer 103 having an electrical insulation property. Moreover, as the material forming the second protective layer 107, iridium as a noble metal is enumerated.
FIG. 8B shows an enlarged cross sectional view of a principal part in the ink jet print head disclosed in Japanese Patent Laid-Open No. 2007-230127. In the ink jet print head of Japanese Patent Laid-Open No. 2007-230127, a heat storage layer 202, a heating resistor layer 208, an electrode layer 216, a protective layer 203, and a supplementary layer 217 are sequentially formed above a substrate 201. Moreover, above the supplementary layer 217, a protective functional layer 218 is formed so as to cover a thermal action portion where the generated heat acts on ink. The heat storage layer 202 is formed from a thermal oxide film, an SiO film, a SiN film, or the like, and once stores the heat generated by the heating resistor layer 208. The heating resistor layer 208 generates heat by being energized, and transfers the heat energy to the ink. The electrode layer 216 is formed from a metallic material and functions as wiring. The protective layer 203 is formed from an SiO film, an SiN film, or the like, and serves as an insulating layer having an electrical insulation property. The supplementary layer 217 is formed from tantalum (Ta) or niobium (Nb), and forms a passive film at the time of electrolytic etching in an electrolytic solution, in order to form the protective functional layer 218 by etching. The protective functional layer 218 is a layer for protecting the heat generating portion from a chemical or physical impact associated with the heat generation of the heating resistor in the heating resistor layer 208. Iridium as a noble metal is enumerated as the material forming the protective functional layer 218.
However, in the case where the protective layer formed from a noble metal is adopted as the protective layer arranged adjacent to the ink reservoir, there is a problem that the adhesion between the protective layer formed from a noble metal and a flow passage forming member is poor.
Usually, the flow passage forming member is joined to a substrate having a heat generating portion arranged therein, whereby an ink flow passage and a liquid chamber are defined in the flow passage forming member. A print head is formed in this manner. Moreover, in cases where a protective layer for protecting the arranged heat generating portion is arranged in the substrate, the substrate and the flow passage forming member are joined together via the protective layer. Accordingly, if the adhesion between the protective layer and the flow passage forming member is poor, then peeling-off might occur between the protective layer and the flow passage forming member. For this reason, in Japanese Patent Laid-Open No. 2007-269011, an adhesion layer is provided between the noble metal and the flow passage forming member so as to improve the adhesion therebetween.
In Japanese Patent Laid-Open No. 2007-269011, as shown in FIG. 8A, the substrate 101 and the flow passage forming member 109 are joined together with the first protective layer 103 and the second protective layer 107 sandwiched therebetween, thereby forming the print head. Here, the second protective layer 107 in the print head of Japanese Patent Laid-Open No. 2007-269011 is formed from iridium as a noble metal, and thus if the second protective layer 107 and the flow passage forming member 109 are joined together as they are, the adhesion between the second protective layer 107 and the flow passage forming member 109 is poor. Accordingly, in Japanese Patent Laid-Open No. 2007-269011, the second protective layer 107 and the flow passage forming member 109 are joined together with an adhesion layer 112 and a resin adhesion layer 113 sandwiched therebetween. Thereby, when the flow passage forming member 109 is joined to the substrate 101, the resin adhesion layer 113 and the flow passage forming member 109 will be joined together. Accordingly, the adhesion between these members is improved and the peeling-off between the substrate 101 and flow passage forming member 109 constituting the print head is prevented.
However, in manufacturing the print head disclosed in Japanese Patent Laid-Open No. 2007-269011, the step of forming the adhesion layer 112 and the resin adhesion layer 113 separately from the step of forming the protective layers 103, 107 is required after the second protective layer 107 is formed above the substrate 101. In order to efficiently transmit the heat generated by the heat generating portion 102 to ink, fewer components between the heat generating portion 102 and the liquid chamber are better. Therefore, a configuration may be contemplated, in which the resin adhesion layer 113 is not arranged between the heat generating portion 102 and the liquid chamber, as with the print head disclosed in Japanese Patent Laid-Open No. 2007-269011. If the resin adhesion layer 113 is not arranged between the heat generating portion 102 and the liquid chamber in this manner, then the step of removing the resin adhesion layer 113 in a region corresponding to the heat generating portion 102 will occur and as a result the number of manufacturing steps might increase further. Accordingly, an increase in the number of steps in manufacturing the print head might increase the time required to manufacture the print head and also increase the manufacturing cost.
Moreover, in the print head disclosed in Japanese Patent Laid-Open No. 2007-230127, as shown in FIG. 8B, above the heating resistor in the heat generating portion, the protective functional layer 218 formed from iridium as a noble metal is arranged so as to cover the bubbling portion. Then, in the print head disclosed in Japanese Patent Laid-Open No. 2007-230127, the protective functional layer 218 is not formed in regions other than the bubbling portion in the heating resistor. In the print head of Japanese Patent Laid-Open No. 2007-230127, the protective functional layer 218 in regions other than the bubbling portion in the heating resistor is removed by etching. Thereby, when the flow passage forming member is joined to the substrate 201, the protective functional layer 218 formed from iridium as a noble metal and the flow passage forming member will not be joined together. Accordingly, the adhesion between the substrate 201 and the flow passage forming member is well secured and the peeling-off therebetween is prevented.
However, in manufacturing the print head of Japanese Patent Laid-Open No. 2007-230127, a step is required, in which the protective functional layer 218 is formed in a predetermined shape so that the protective functional layer 218 may not come in contact with a joint portion between the substrate 201 and the flow passage forming member. In Japanese Patent Laid-Open No. 2007-230127, the protective functional layer 218 is formed in a predetermined shape by removing portions corresponding to regions other than the bubbling portion in the protective functional layer 218 by etching. For this reason, the time required to manufacture the print head might increase by the time of the step of forming the protective functional layer 218 in a predetermined shape, and the manufacturing cost might increase.